A 42-year-old man being questioned over the murder of UDA boss John Boreland on Sunday was released by police last night.

The father-of-three was blasted in the head with a sawn-off shotgun as he got out of his car on Sunningdale Gardens, off the Ballysillan Road.

A leading member of the terror gang, Boreland - known as 'Bonzer' - had been aware that his life was in danger.

He had been approached a fortnight ago by two men who warned: "You don't know what's coming."

Concerns are mounting that his murder could mark the beginning of a bloody loyalist feud.

People close to Boreland last night accused members of the UDA in south Belfast of ordering his shooting as part of a turf war between factions.

Boreland, who served a prison sentence for extortion, escaped a UDA murder bid two years ago when he was shot in the thigh. He and his close UDA associate Andre Shoukri were shot at by a rival loyalist gang.

Police had warned the father-of-three in recent months that his life was under threat.

Detective Chief Inspector Justyn Galloway confirmed that the main line of enquiry was "tensions within loyalism".

Mr Galloway added: "He was known to police and had been the victim of a previous shooting in 2014 and was aware he was under threat at the time of his murder... we are clearly looking at tensions within loyalism at this time."

Solicitor John McBurney - a member of an independent panel tasked with assessing paramilitary groups - warned there could be "tit-for-tat" attacks. "Belligerence and entrenchment could take groups into battle in a way that is completely counter-productive to any progress moving away from paramilitarism," said Mr McBurney.

Alliance policing spokesperson Stephen Farry MLA said the murder was a reminder of the grip paramilitaries have over many communities across Northern Ireland.

"While we welcomed the report of three-person panel on paramilitarism, the subsequent response from the Executive has been weak. What was termed an action plan is vague in many respects, and lacks sufficient timescales and targets.

"It falls well short of being a strategy with a clear-cut analysis of the underlying problem and sense of shared ownership of a desire to root out paramilitarism and organised crime.

"In particular, there needs to be much more urgency given to putting in place a protocol on the 'dos' and 'don'ts' of how public agencies such as the PSNI and Housing Executive interact with paramilitary structures that does not inadvertently reinforce them but actually breaks them down."

Although he knew he was under threat, Boreland did not change his routine.

"A week or so ago he was threatened by those connected with the UDA in south Belfast," the source said.

"They told him: 'You don't know what's coming'. But he took it with a pinch of salt.

"He never changed his routine. He was shot five minutes after he left the pub on Sunday night.